Pharmacological stress: a useful exercise?

Over the past years cardiovascular magnetic resonance (CMR) imaging has been increasingly used to detect the presence of coronary artery disease and to assess its functional consequences to the myocardium [1]. Several approaches have been applied to detect coronary artery disease with CMR including direct visualization of coronary arteries and bypass grafts [2– 4] (magnetic resonance coronary angiography), the characterization of myocardial tissue [5–8] (delayed contrast enhancement) or the visualization of the effects of induced ischemia [9–17] (wall motion analysis or perfusion measurements). The latter is particularly valuable in clinical decision making since the detection of epicardial coronary luminal narrowing alone does not necessarily predict its hemodynamic consequences to the underlying myocardium. In the last decades, pharmacological stress has been extensively evaluated as an alternative stress method and is particularly advised to those patients who are not able to perform adequately either due to limited exercise capability or a disabling disease. With the development of rapid gradient systems and the routine application of advanced CMR scanner systems, it has become possible to perform cine imaging of the heart at rest and under stress conditions with CMR. Since space is limited within the MR scanner bore and patient movement impairs image quality, pharmacological stress is preferred for CMR imaging. Research efforts have been focused on the definition of the clinical role of magnetic resonance pharmacological stress for the detection of inducible wall motion abnormalities, preferably using dobutamine stress magnetic resonance (DSMR) [18–30]. High-dose DSMR proved to be highly accurate for the detection of inducible wall motion abnormalities and its usefulness for determination of patient prognosis has been shown [18–24]. DSMR at low-dose dobutamine levels was found to be highly predictive of functional improvement of resting wall motion abnormalities after coronary revascularization procedures (detection of viable myocardium) [25–27]. For induction of ischemic wall motion abnormalities, adenosine/dipyridamole or dobutamine are routinely used and the outcome is often considered alike and interchangeable. In a landmark study by Paetsch et al. [31], the results of a direct comparison of dobutamine stress CMR, adenosine stress CMR and adenosine stress CMR perfusion as assessed during a single, combined examination with all stress tests were evaluated against coronary angiography as the standard of reference. This study proved that dobutamine was superior to adenosine stress for the detection of inducible wall motion abnormalities related to the presence of epicardial coronary Editorial comment to the paper of Karamitsos et al. (doi: 10.1007/s10554-008-9392-3).